1. Field of the Invention
This invention relates in general to railway cars and, more particularly, to a depressed center beam flat car.
2. Description of the Prior Art
At present lumber and other construction material is conventionally transported by railroads in center beam/center partition railcars, generally having a 100 ton nominal capacity built to conform to the Association of American Railroads (AAR) Plate "C" clearance. The distance between end bulkheads of these cars is generally sixty or seventy three feet, and the tare or empty weights range from 63,000 to 69,000 pounds. Cars with tare weight in the foregoing range respectively have lading carrying capacities ranging from 200,000 to 194,000 pounds. The center beam/center partition design permits the construction of lightweight cars with long spans between bulkheads, such as in the previously described car having a length of seventy three feet.
The lumber and the like that is transported in center beam/center partition cars is commonly made up of equal length pieces banded together in modules. The lengths of the modules range from eight to thirty two feet in increments of two foot lengths and nominal four foot widths. The actual width of lumber modules varies according to nominal dimensions of 2".times.4", 2".times.6", 2".times.8", 2".times.10", and 2".times.12". The height of each module is a constant twenty four inches. The transported lumber is normally air dried having an average density of approximately 31.5 pounds per cubic feet.
The lumber modules can be stacked up to five high on both sides of the center beam/center partition cars. Due to its length between bulkheads, the center beam/center partition car having a seventy-three foot length is preferred over other sizes, because it accomodates a large combination of lengths of lumber and the like. The weight of typical loads of lumber in known center beam/center partition cars in a fully loaded condition is approximately 170,000 pounds. Inasmuch as a standard 100 ton center beam/center partition cars possesses a carrying capacity of 194,000 to 200,000 pounds as stated previously, such existing cars only achieve a payload efficency in the range of 85% to 87.6%.
Center beam/center partition cars of the foregoing design have a center of gravity of approximately ninety-six inches loaded and fifty-six inches empty. The center structure of those cars requires that during loading and unloading, materials must be placed and removed to even weight levels on each side of the center structure to avoid unbalanced loads which can cause the cars to tip-over with the result that lumber modules could be hurled to the ground in various directions like projectiles. Written warnings are clearly stencilled on these existing cars stating that uneven loading and unloading at the sides of the cars can cause tipping of cars sideways. Thus, such standard cars present the potential of damage to the lumber and equipment, and possible safety hazards for personnel during the loading and unloading of materials. Further, the high center of gravity of the loaded car in the prior art produces relativily poor track worthiness and ride stability. Therefore, it is desirable to provide center beam/center partition cars that not only provide greater efficency, but also demonstrate greater stability during loading/unloading and when being transported.